Electric lamp and method of making the same.



APPLICATION FILED NOV. 17, 1902.

Patented Jan. 26, 1909.

2 SHEETSSHEET 1.

Fig.4.

Ihventor. Ch arles P. Steinmetz.

Witnesses.

G. P. STEINMETZ. ELECTRIC LAMP AND METHOD OF MAKING THE SAME.APPLIOATION FILED NOV. 17, 1902.

910,736. Patented Jan. 26, 1909.

Z SHEETS-SHEET 2 Witnesses. Inventor.

Charles P. Steinmetz.

' To all whom it may concern:

-' terminals crane lam them in suflicient quantities.

UNITED STATES PATENT OFFICE.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGN OR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK. ELECTRIC LAMP AND lIETHODOF MAKING- TEIE SAME.

Patentedil'an. 2c, 1909.

Application filed November 17, 1902. Serial No. 131,660.

Be it known that I, CHARLES P. STEIN- METZ, a citizen of the UnitedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements in Electric Lams and Methods of Making the Same, of whic the following is aspecification.

I have found that the 0 eration of electric lamps of that type of w ichthe so-called mercury arc lamp is the best known exampie is muchimproved if they are run at igher tem eratures than those which have'heretofore een practiced. If mercury be employed as the volatileelectrode the color of the light improves as the temperature of the lampincreases. Moreover, if the lam is run at a higher temperature othersubstances, such as lithium, potassium, magnesium, sodium, and variouscombinations of these metals may be added to the mercur by which thequality of the light can be st' 1 further improved. In place of usinginercury or substances containing mercury, other materials having acomparatively low boiling point may be em loyed to form the va or1z1ngelectrode of tlie lamp. If these su stances are employed in the vaporarc lamp running at the temperatures which ave heretofore been commonlyemployed, the advantages due to their lightgiving power are onlypartially obtained as the tem perature is not high enough to volatilizeAnother advanta e, which res ts from the employment of high temperaturesin lamps of this character, is due to the fact that with suchtemeratures, the drop in voltage between the amp terminals necessary inorder that the lamp may be used on ordinary circuits can be obtainedwith a tube which is considerably shorter than those heretoforeemployed. The limit to the temperature at whlch it has heretofore beenpossible to run these lamps has been given by the heat-resisting ower ofthe lass tube formin the Walls 0 the exhausted chamber in whic the areplaced. I have found that ifthe wa or walls of the exhausted chamber, orat least of that portion of it surrounding the light iving are, are madeout of fused quartz, t e temperature at which the lamp can be 0 eratedis greatly increased, and that thereby the above noted advantages due tosuch an increase in temerature can be obtained. Tubes formed of usedquartz will stand heatin to a much hi her temperature without so 'teningthan wil glass tubes, moreover rapid and extreme changes of temperaturedo not have the tendency to' crack the tubes which exists with glasstubes under such conditions.

In the accom anying drawings I have illustrated severa embodiments of myinvention.

In the drawings Figure l is a sectional elevation showing oneconstruction of lamp; Fig. 2 is a partial sectional elevation showing aslight'l modified construction; Fig. 3 is a sectiona elevation showing asomewhat different construction of lamp; Fig. 4 is a diagram showing therelative proportion of the different materials composing the lamp tubeshown in Fig. 3; Fig. 5 is a sectional elevation showing a paratusemployed in the manufacture of amp tube shown in Fig.3; and- Fig. 6 is aplan view showing the same ap aratus.

n the construction shown in Fig. 1, a light-transmitting tube 1 made outof fused quartz forms the inclosing chamber of my lamp. A solid terminal2 is placed at the upper end of the tube. At the lower end of the tube amass of materialB, such as mercury, or a mercury amalgam containingvarious substances which va orize at the temperature employed, or theikc, is placed and forms the other main electrode. The tube 1 isprovided at its lower end with an off-shoot 4 and in this oil-shoot 4 isplaced another mass 5, similar to the mass 3, forming an auxiliary orstarting electrode. The lower end of the tube 1 and the oii-shoot 4 areshaped to form comparatively small tapered necks 6, and on the outsideof these tapered necks are fitted caps of metal 7. The outer surface ofthe necks 6 and the interior surface of the caps 7 may be ground to formair-tight joints. The metal caps are in electrical contact with themercury and have suitable current-carrying leads connected to them. Themetal out of which I form the caps 7 is a mixture of nickel with iron orsteel, the amount of nickel in the composition being about 35% to 37 Iemploy; this mixture as its thermal coefiicient of expansion isapproximately equal to the thermal coefiicient of expansion of thequartz, which is very small, being much less than that of glass.

llO

Iemploy the joint described owing to the difliculty of making a sealedjoint such as is employed with glass tubes due to the efiect the caps 7.The tube is ground interiorlyat 10 and the plug 9 is inserted to make atight fit. Above the portion 10 the end of the tube may be flared toform a chamber 11 in which a quantity of mercury is placed to sealthejoint. not be ,mte a1 with the tapered plug 9. Preferabl t e terminal 2and the plug 9 are connecte by a portion 12 considerably smaller indiameter than the tcrminal 2 in order that the heat conducted from theterminal 2 to the plug 9 ma be diminished. The tube 1 is exhausted in t0 same manner as has heretofore been em loyed in exhausting glass tubes.At 13 I ave indicated the fused oif exhaust tube..

In Fig. 2 I have shown a slightly difi'erent method of closing the upperend of the tube. In this construction a cap 9, similar to the cap 7shown-at the lower end of Fig. 1, is employed at the upper end of thetube. The solid-terminal 2 is connected thereto by a slender portion 12as in Fig. 1. The upper end of the quartz tube may be'shaped to receivea mercur seal, desired.

Instead of orming the tube entirely of quartz and forming metallic endconnections as above described, the tube may be made with its bodyportion of fused quartz and its end portions of some different substanceinto which metallic leading-in wires can befused in the ordinary mannerheretofore practiced in making tubes for lamps of this character. InFig. 3 I have shown a lamp of this character similar in its eneralarrangement to the lamp shown in ig. 1, but in which the portion of thelamp tube 1 be-. tween the lines A A and B B 1s formed of fused quartz,while the terminal portions beyond the lines A A and B B respectivelyare formed of a material containing silica,-

united with various other substances; for instance, otassium and calciumhydroxid may be a ded to the fused uartz to make the terminal ortions oft e lamp. The potassium an calcium hydroxid or other substances, whichare united with the silica to form the terminal portions of-the tube,

should be added in such manner that the roportion of these substancesshould vary from zero at the lines A A and B B respecrovided Theterminal 2 may or may-- tivelyto an amount sufiicient to form a glassinto which a platinum wire can readily be sealed, as shown, and havingpractically the same thermal coefiicient of expansion as platinum at theend.

In Fi 4 I have shown a diagram illustrating t e proportion of thematerials in the com osition of the tube 1. In this diagram the e D D isequal to the length of the tube 1 and the amount of quartz which isfound in the tube at any point along its length is Ernoportional to thedistance betweenthe e O B A C and the line D D at the correspondingpoint. -The amount of other materials employed to form the terminalportions of the tube are indicated by the distance between correspondingpoints onthe lineCBAC andon thelineEBAE.

It will of course be understood that the quartz and other materials areintimately mixed and are not separated by any distinct line of cleavageas might appear from the diagram. With a tube as thus constructed, themechanical resiliency of the tube is sufficient to take up thediiference in the.

thermal ergiansion of the tube at the lines A A and B reslpectively andthepoints where the termina wires are se led in.

In forming the lam tubes above described, the following metho may befollowed: A refractory conductor such as carbon may be embedded in amass of quartz granules or silica in other finely divided states. On thepassage of a heavy electric current through the conductor, heat isproduced sufiicient to fuse the quartz in the vicinity of the conductor,whereupon when the conductoris cooled :a shell of fused quartz is formedsurrrounding the conductor. In Figs. 5 and 6 I have illustrated anarrangement by which such tubes may be formed. In these dra s the carhon-heating conductor 14 has su stantially the shape which it is desiredto give the inside of the tube. The conductor 14 is connected at itsends to heavy metallic conductors 14 which {are mounted in the wall 15of the furnace chamber. Filling the lower part of the chamber 15 andsurroun 14 is a mass of the material w 'ch it is desired to fuse inorder to form a tube. At 16 I have indicated the appearance of such atube after forming.

- When the tube is formed entirely of fused quartz as in Fig. 1 it willof course be understood that the material 17 surrounding the conductoror core 14 is all silica, but when it is desired to form a tube likethat in Fig. 3 the material surrounding different ortions of the corewill be different. Only t at ortion of the heating chamber between thees A A and B B, which correspond in position with reference to the tubeto'the lines A A and B B of Fig. 3, will be filled with uartz alone.Portions between the lines A A, B and the adjacent ends of the casingwill be filled with the conductor,

a mixture containing other materials: That is, with the tube abovedescribed, the uartz will be mixed with potassium and ca cium hydroxidand the mass of otassium and calcium hy droxid will be gra uated in thespace between the lines A A and B B and the adjacent ends of the casingas indicated in Fig. 4

The rough tube-blank obtained in the heating chamber may have the carboncore burned out and be worked into a finished form by heating in theelectric are or other source of great heat.

The operation of the lamp is as follows: At starting, the solid terminal2 and the vaporizing terminal 5 are connected to one side of the supplycircuit, while the main vaporizing terminal is connected to the otherside of the line. If, now, the tube be agitated slightly so as to causethe metal forming the terminal 3 to contact with metal forming theterminal 5, an initial vaporization takes place and the vapor thusformed enables the current to pass from the terminal 3 to the terminal2. After starting, the auxiliary terminal may be cut off if desired. Theterminal 2 may have an extension 2 preferably formed of a carbonfilament depending from it to a point slightly above the surface of themercury 3 to assist in starting the are if desired.

If the substance employed to form a vaporizing compound is not fluid atordinary temperatures, other means for starting the lamp may beemployed, as for example those shown in British Patent #5545 of 1903.

While I have illustrated and described the best form of my inventionwhich is now known to me, I do not intend to be limited to the detailsof construction shown and described as I consider my invention in itsbroader aspects to be inde endent of such features of construction an toconsist in an inclosing chamber for electric lamps made out of fusedquartz.

In a divisional a plication, Serial No. 455,110, filed Se tem er 28,1908, claims are made on an enve op having a body portion of fusedquartz and an end portion of a different material. f

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. In a vapor electric device, an inclosing chamber formed out of fusedquartz and provided with means for conducting current thereinto.

2. In a vapor electric device, an inclosing chamber formed out of fusedquartz, and connections therefor formed out of a composition of nickeland steel.

3. In a vapor electric device, an inclosing chamber formed out of fusedquartz, and connections therefor formed out of composi tions of nickeland steel or iron, the nickel forming about 37% of the composition.

4. In a vapor electric device, an inclosing chamber having the portionsubjected to the heating action of the vapor are formed out of fusedquartz.

5. In a vapor electric device, an exhausted chamber thelight-transmitting walls of which are made of fused quartz, said chamberhaving means for conducting currenttheremto.

In witness whereof, I have hereunto set my hand this 15th day ofNovember, 1902.

CHARLES P. STEINMETZ.

Witnesses:

BENJAMIN B. HULLf HELEN ORFORD.

